Process and device for desulphurizing hydrocarbons containing thiophene derivatives

ABSTRACT

The invention relates to a selective desulphurisation method for thiophene derivatives contained in the hydrocarbons emitted from the distillation of crude oil, refined or not, consisting in oxidising the atoms of thiophene sulphur in sulphone in the presence of an oxidising agent and separating the sulphonated compounds from said hydrocarbons. This inventive method comprises at least one first stage involving the oxidation/absorption by heterogeneous catalysis of the sulphurous compounds in an organic environment, at a temperature of at least 40?C, at atmospheric pressure in the presence of an organic oxidiser from the family of peroxides and peracids, in the presence of a catalyst having a specific surface area greater than 100 m2/g and a porosity varying from 0.2 to 4 ml/g, and a second stage wherein the used catalyst is regenerated.

The present invention concerns a process and a device for desulfurizinghydrocarbons, and particularly, for desulfurizing fuel bases forgasoils, kerosenes, and gasolines. In particular, it concerns thedesulfurization of fuel bases containing dibenzothiophenic compounds.

The presence of sulfur in fuels constitutes what is considered today tobe a major problem for the environment. Indeed, through combustion,sulfur is converted to various sulfur oxides that can be transformedinto acids, thus contributing to the formation of acid rain.

In general, refineries use catalytic hydrosulfurization processes toreduce the sulfur content in fuels.

Thus, gasoils derived directly from distillation are hydrotreatedbetween 300° and 400° C. under pressure of hydrogen varying between 30and 100 bars (30 to 100·10 ⁵ Pa), in the presence of a catalyst on afixed bed and composed of sulfides of metals of groups VIb and VIIIdeposited on aluminum oxide, for example cobalt and molybdenum sulfidesor nickel and molybdenum sulfides. Because of the operating conditionsand the consumption of hydrogen, these processes can be costly both ininvestment and in operation, particularly if fuels with very low sulfurcontent are to be produced. Consequently, in order to desulfurize a fuelinitially containing 1% sulfur by weight until it has a concentration ofsulfur of between 0.05 and 0.005% by weight, the size of the reactor canbe multiplied by four and the quantity of hydrogen needed for thereaction must be increased by about 20%. It is particularly difficult toeliminate traces of sulfur by such processes, especially if the sulfurbelongs to refractory molecules such as alkyl dibenzothiophene inposition 4, or 4 and 6.

In some countries like Sweden, the United States, particularly inCalifornia, and others, the total sulfur content of gasoils is alreadylimited to 0.005% by weight. This limitation could become generalized intime within the OECD countries. For Europe, this goal of 0.005% byweight of total sulfur could be achieved in 2005.

Unlike gasoils, gasolines are not only distilled directly from crudeoil, these gasolines being then slightly sulfurous, but can also beobtained by several processes such as reforming of naphthas,isomerization of light naphthas, alkylation of butane or propaneproducing isooctane, methoxylation of isobutene, and the catalyticcracking of distillates under vacuum or atmospheric residue. Inparticular, catalytic cracking provides between 20% and 60% by weight offinal gasoline. However, these gasolines contain up to 0.1% by weight ofsulfur. It is common, therefore, to desulfurize gasolines produced bycatalytic cracking using processes similar to those described for thehydrodesulfurization of gasoils, for which the operating conditions ofhydrogen pressure, space velocity, and temperature are more stringent.These processes, although costly, do not enable total sulfur content incracked gasoline of between 0.005% and 0.03% by weight to be obtained byconventional means. Although refiners, in order to reduce this sulfurcontent, have thought that including additives in the cracking catalystwould break down the sulfurous compounds formed during the process,particularly mercaptans and sulfides, these additives have only alimited or even no effect on the benzothiophenic derivatives, even whenthe mercaptans and the sulfides have been eliminated before cracking.

In the case of gasolines from catalytic cracking that generate sulfur ingasolines, hydrodesulfurization is not only ineffective with respect tothiophenic compounds, but it is also destructive with respect to theoctane index of the gasoline. Indeed, during the hydrodesulfurizationreaction, there is a partial hydrogenation of the olefins contained inthese cracked gasolines, their disappearance resulting in a decrease inthe octane index of the gasoline and thus a deterioration in the qualityof the gasoline. To compensate for this loss, it is possible tointroduce other components to improve this index or to reprocess thegasoline itself to increase this index. The inclusion of an additive orthe reprocessing to improve the quality of the gasoline affects theproduction cost that much more, and it is therefore advantageous to havea processing method that enables the direct elimination of therefractory sulfurous compounds, such as benzothiophenic derivatives, bylimiting the use of hydrogen.

Processes for selective oxidation of sulfurous compounds are amongtreatment processes that can achieve this end. Among the methods andprocesses developed to reduce the quantity of sulfur in fuels in theform of derivatives of thiophene, oxidation by organic peroxides,organic hydroperoxides, hydrogen peroxide, and organic peracids, hasbeen considered either without catalyst, or by homogenous catalysis inthe presence of catalysts based on organometallic compounds or metallicoxides in aqueous phase (see U.S. Pat. No. 3,668,117, U.S. Pat. No.3,565,793, EP 0,565,324, and publications by T. A. KOCH, K. R. KRAUSE,L. EMANZER, H. MEHDIZADEH, J. M. ODOM, S. K. SENGUPTA, New J. Chem.,1996, 20, 163-173, and by F. M. COLLINS, A. R. LUCY, C. SHARP, J. ofMolecular Catalysis A: Chemical 117 (1997), 397-403).

Processes using molybdenum- and tungsten-based metallic catalysts in thepresence of hydrogen peroxide in aqueous solution (heterogeneouscatalysis) take place at temperatures of more than 60° C., and there isexcessive consumption of hydrogen peroxide, a part of this oxidant beingbroken down by the catalyst used. The peracids used, very powerfuloxidants, obtained by reaction of hydrogen peroxide and a carboxylicacid such as formic acid or acetic acid, are generally less effectivethan hydrogen peroxide and less selective with respect to sulfurouscompounds and in particular can oxidize olefins.

Other oxide sulfurization processes in organic medium have beenproposed. They consist of placing in contact powdered metallic oxides,or of forming metallic compounds having peroxo groups in aqueous ororganic solutions with the hydrocarbons containing these refractorysulfurous compounds, whether or not in the presence of organic oraqueous peroxides which are introduced with an alcohol type solvent orin the water (see U.S. Pat. No. 3,816,301, U.S. Pat. No. 4,956,578, U.S.Pat. No. 5,958,224).

Another process, described in U.S. Pat. No. 3,945,914, consists ofproducing a desulfurized hydrocarbonated material in three processingsteps. The first step consists of at least partially oxidizing thesulfurous compounds by placing them in contact with peroxides in thepresence of metallic catalysts containing metals from the groupincluding titanium, zirconium, molybdenum, tungsten, vanadium, tantalum,chromium, and their mixtures, in liquid or solid form possiblysupported, although the supports are not essential for the reaction. Thesecond step consists of placing the hydrocarbonated material containingthe oxidized compounds in contact with another metallic component,metallic oxide or peroxide (metals from the group including nickel,molybdenum, cobalt, tungsten, iron, zinc, vanadium, copper, manganese,mercury, and their mixtures), at a temperature varying from 250° C. to730° C., under hydrogen pressure. The third step consists of recoveringthe desulfurized hydrocarbonated material.

In all these methods and processes, the derivatives of thiophene intheir sulfonated and/or sulfonic form are transformed. However, for someof these compounds, even when working at high temperature, the reactionis relatively slow and total conversion is not achieved in less than onehour, except by using very strong concentrations of oxidant, often fargreater than the quantities necessary for the oxidation of the sulfurousderivatives. In other cases, it is possible to work in several steps,but they are costly in time and in monitoring the unit.

The present invention therefore proposes a process for desulfurizinghydrocarbons, particularly those used as bases for fuels containingthiophenic derivatives, without reducing the index of the octane numberor of the cetane number, sometimes even increasing these indices. Inparticular, it concerns the finish treatment of hydrotreated gasoils,kerosenes, and catalytic cracked gasolines with high concentrations ofrefractory thiophenic derivatives in hydrogenations.

Furthermore, the invention proposes such a process that makes itpossible to reach oxidation levels that are identical if not greaterthan the known processes, while limiting the reaction and separationtimes of the oxidized sulfurous compounds from the desulfurizedhydrocarbons.

An object of the present invention is therefore a process forselectively desulfurizing the thiophenic compounds contained in thehydrocarbons produced from the distillation of crude oil, refined ornot, consisting of oxidizing the thiophenic sulfur atoms into sulfonesin the presence of an oxidizing agent and a catalyst, and of separatingthe obtained sulfonated compounds from said hydrocarbons, this processbeing characterized in that it comprises at least a first step ofoxidation/adsorption by heterogeneous catalysis of the sulfurouscompounds, in an organic medium, at a temperature of at least 40° C., inthe presence of an organic oxidizer from the family of peroxides andperacids and in the presence of a catalyst having a specific surfacearea greater than 100 m²/g and a porosity varying from 0.2 to 4 ml/g,and a second step of regeneration of the used catalyst, the regenerationstep always following the oxidation/adsorption step.

Within the scope of the present invention, derivatives of thiophene areunderstood as being benzothiophenic, polybenzothiophenic compounds andtheir alkyl derivatives, among which are the alkyldibenzothiophenes,particularly refractory to the conversion processes usually used byrefiners.

The process of the invention has the advantage, on the one hand, ofensuring the oxidation at atmospheric pressure of all of the sulfurcontained in the hydrocarbons, and more selectively a conversion of thethiophenic derivatives into sulfones, this by means of a simpleindustrial process, and on the other hand, of simultaneously adsorbingthese sulfoxide compounds on the catalyst. In fact, the separation ofthe hydrocarbons from most of the formed sulfones and sulfoxides isimmediate, with the latter ending up in solid form deposited on thecatalyst or deposited in a form that can be filtered by known means, inthe treated hydrocarbons. This catalyst, on which these sulfoxidecompounds have been absorbed, constitutes the “used catalyst.” Thesulfones that may have been dissolved in the treated hydrocarbons can beextracted. Moreover, this oxidation/adsorption has no effect on theolefins, which in catalytic cracked gasolines does not change the octaneindex, or the concentration of unsulfurous aromatic compounds. Inaddition, the oxidation process according to the invention improves thecetane number of the gasoils.

Without being limited by a theory, it has become clear that the greaterthe specific surface area of the catalyst, the longer it remains active.

Furthermore, because compounds of the sulfone and sulfoxide type have astrongly polar nature, they are kept on the surface of the catalyst,probably at the catalyst's Lewis acid sites. In addition, the larger thesize of the pores, the less the catalyst's pores risk becoming quicklyclogged and the greater the longevity of the catalyst during theoxidation cycle. For the present invention, one has to select thecatalyst that has the best compromise of specific surface area and poresize to obtain sufficient activity, for as long as possible, to be themost effective for oxidation/adsorption.

When the process is continuously implemented intermittently, theoxidation/adsorption and regeneration steps can be performed in the samereactor or simultaneously in reactors arranged in parallel and operatingalternatively for one or the other of the fixed bed steps, or in atleast two moving-bed reactors connected to each other by the catalyticbed, one being used for oxidation/adsorption and the other forregeneration.

With a fixed bed, the first reactor containing a fixed catalyst bedreceives the flow of hydrocarbons and oxidizing agent and the secondreceives, for the regeneration of the catalyst, liquid effluents, suchas a washing solvent, or oxidizing gaseous effluents like air or anair/N₂ mixture, the temperature of the catalytic bed being increased.These reactors change function when the effectiveness of the catalyst inthe oxidation/adsorption reactor is no longer sufficient in oxidationand/or adsorption.

With a moving-bed, the hydrocarbons are brought into the first reactorwhere the oxidation takes place, the catalyst being pushed progressivelytoward the second reactor where it is regenerated before being returnedto the oxidation/adsorption reactor. The moving-bed reactors, well knownparticularly in the area of reforming, can be used in this device. Inthis form of embodiment, a third reactor is used, placed between thefirst two reactors and making it possible to eliminate the hydrocarbonsfrom the used catalyst before washing it or burning off the trappedsulfone and sulfoxide compounds.

The catalysts used according to the present invention are selected amongthe supports from the group consisting of silicas, aluminum oxides,zirconias, amorphous or crystalline aluminosilicates, aluminophosphates,mesoporous silicic and silicoaluminate solids, activated carbon andclays, these supports being used alone or in mixture. In the catalystsof the invention, these supports can be used advantageously as supportsof metals of the group consisting of titanium, zirconium, vanadium,chromium, molybdenum, iron, manganese, cerium, and tungsten; thesemetals in oxide form can be introduced into the matrix of the support ordeposited on the surface of the support. In fact, a synergistic effecthas been noted of the metal with the support, that is, an unexpectedincrease of activity of the catalyst with respect to the oxidation ofthe thiopenic compounds, and at the same time, an increased trapping ofthe sulfone and sulfoxide compounds in the pores of the catalyst,without any of them being subsequently desorbed.

In the process according to the invention, the catalyst contains from 0to 30% by weight of metal in oxide form on at least one support.Preferably, the catalyst contains from 0 to 20% metal in oxide form.

Among the supports composed of refractory oxides, gamma-aluminum oxides,silicon oxides, silicic mesoporous solids, and silicoaluminates arepreferred.

Among the supported catalysts, catalysts containing tungsten or titaniumin oxide form are preferred, deposited on a support or introduced intothe matrix, this support being selected from among the silicon oxides,aluminum oxides and aluminosilicates, alone or in mixture.

In a preferred form of implementation of the process, the totaloxidizer/sulfur mol ratio contained in the hydrocarbons is between 2 and20, and preferably between 2 and 6.

According to the invention, the oxidizers are selected from among thecompounds with the general formula R₁OOR₂, in which R₁ and R₂ areidentical or different, selected from among hydrogen, linear or branchedalkyl groups having from 1 to 30 carbon atoms and aryl or alkylarylgroups the aryl motif of which can be replaced by alkyl groups, while R₁and R₂ cannot be hydrogen simultaneously.

In a preferred embodiment, the oxidizer of the formula R₁OOR₂ isselected from the group consisting of tert-butyl hydroperoxide anddi-tert butyl peroxide.

Other oxidizers of the invention, the peracids of formula R₃COOOH, areselected so that R₃ is hydrogen or a linear or branched alkyl grouphaving from 1 to 30 carbon atoms. They are preferably selected from thegroup consisting of peracetic acid, performic acid, and perbenzoic acid.

In the process of the invention, the catalyst regeneration step consistsof eliminating the formed deposits by washing or combustion.

For the washing, a solvent is used, preferably polar, from the groupconsisting of water, linear or branched alcanols having from 1 to 30carbon atoms, alone or in mixture with water, alkylnitriles having from1 to 6 carbon atoms. Water, acetonitrile, methanol, and their mixturesare preferred.

By combustion, the catalyst is brought up to a temperature of no morethan 800° C., preferably a temperature equal to or less than 650° C.,under a pressure varying from 10⁵ Pa to 10⁶ Pa, preferably from 10⁵ Pato 2×10⁵ Pa, in the presence of an oxidizing gas. Oxidizing gas isunderstood as being pure oxygen and all mixtures of gas containingoxygen, particularly mixtures of oxygen and nitrogen and air itself. Thequantity of oxygen in the nitrogen is adjusted in order to limit theformation of water vapor, since too great a quantity of water vapor hasthe side effect of modifying the structure of the pores of the catalystby decreasing their volume, specifically when it contains crystallinealumunosilicates such as zeolites or alumuninophosphates as support.Moreover, this adjustment makes it possible to control the temperaturevariations related to the exothermicity of the combustion.

A second object of the invention is a device for implementing theprocess defined above, this device comprising at least a first reactorcontaining an oxidation catalyst and having feed pipes for thehydrocarbons and the oxidizer and an outlet pipe for the desulfurizedhydrocarbons, and possibly a second reactor having feed pipes forsolvent or oxidizing gas of the catalyst, in order to regenerate it, andan outlet pipe for the combustion gases. Oxidizing gas is understoodhere as oxygen/air, air/nitrogen, and oxygen/nitrogen mixtures.

When the device includes two reactors, the reactors can operate with afixed bed or a moving bed.

A third object of the invention is the application of the processdefined above to the specific finish treatment of gasolines producedfrom catalytic cracking, or the treatment of gasoils having beenpreviously hydrotreated and kerosenes, for better economy of theprocess.

The invention will now be described in more detail, with reference tothe appended drawings in which:

FIG. 1 is a diagram of a device with two reactors operatingalternatively for oxidizing and for regenerating the catalyst;

FIG. 2 is a diagram of a device having two moving-bed reactors, thefirst corresponding to the oxidation step, the second to the catalystregeneration step, a pipe for return of the regenerated catalyst beingadded to the system;

FIGS. 3-1 and 3-2 show graphs illustrating the total sulfur content, asa function of time, of the hydrocarbons treated according to theinvention in the Example III below.

The device of FIG. 1 has two reactors 1 and 2 charged with a catalystarranged as fixed-bed. When the reactor 1 is operating in oxidation andthe reactor 2 operates in regeneration, the pipe 3 takes the sulfuroushydrocarbon load, into which the oxidizer has been introduced by thepipe 4, the three-way valve 6 a and the pipe 8 a. The flow ofdesulfurized hydrocarbons leaves the reactor 1 by the pipe 9 a andreaches the desulfurized hydrocarbon outlet pipe 10 a via the three-wayvalve 7 a.

At the same time, the pipe 5 takes to the reactor 2 either anappropriate solvent or an oxidizing gas, via the three-way valve 6 b andthe pipe 8 b. When the reactor operates in combustion, the temperatureof the catalytic bed is held at 500° C. The solvent containing thesulfones recovered on the catalyst or the combustion gases, primarilySO₂, CO, and CO₂, are evacuated via the pipe 9 b, the three-way valve 7b and the pipe 11 b in the pipe 11 a.

When the regeneration of the catalyst is done and the activity of thecatalyst of reactor 1 becomes insufficient, the function of the tworeactors is exchanged. Thus, the hydrocarbons/oxidizer mixture passesthrough the pipe 3 a and the valve 6 b to enter the reactor 2. Thedesulfurized hydrocarbons are removed by the pipe 9 b and are taken tothe outlet pipe 10 a via the valve 7 b and the pipe 10 b.

At the same time, the solvent or the oxidizing gas arriving by the pipe5 is sent to the reactor 1 by the pipe 3 a, the valve 6 a and the pipe 8a. The solvent or the oxidation gases are taken back in the outlet pipe11 a via the pipe 9 a and the valve 7 a.

The valves 6 a, 6 b, 7 a, and 7 b can be exchanged according to a commonprocedure, in order to allow the circulation of the proposed flows.

A filter can be placed advantageously on one of the pipes 9 a or 9 b, oron 10 a or 10 b, to recover the solid sulfones formed during oxidationand remaining in suspension in the hydrocarbons. Sulfur traps equippedwith absorbents such as silica or activated alumina can beadvantageously added to these same pipes, downstream from these filters,to trap sulfones that are still dissolved in the treated hydrocarbons.

The device of FIG. 2 includes two reactors 20 a and 20 b, arranged inseries, each containing a moving-bed catalyst, the reactor 20 aoperating in oxidation mode and the reactor 20 b operating inregenerative mode, and a propulsion device 30 to allow the catalyst fromthe reactor 20 b to return to the reactor 20 a.

The hydrocarbons are taken by the pipe 40 into the reactor 20 a, afterhaving been doped by the oxidizer via the pipe 50. For example, thereactor 20 a can be selected from among funnel-shaped reactors, themoving bed of the catalyst being moved by gravity toward the lower partof the reactor. In this way, while the desulfurized hydrocarbons areremoved by the pipe 60, the catalyst is forced by gravity into thereactor 20 b through the pipe 70. The solvent or combustion gas isintroduced via the channel 80 in the reactor 20 b. In order to effectregeneration by combustion, the temperature is increased to and held at500° C. The sulfones-containing solvent or the combustion gases areremoved by the pipe 100.

Since these moving-beds generally operate intermittently, the catalystnot being moved continuously, it is beneficial to place on the reactor20 b a solvent or nitrogen purge to eliminate the hydrocarbons prior towashing, and/or eliminate the combustion gases by stripping thenitrogen.

When it leaves the reactor 20 b, the regenerated catalyst is taken viathe pipe 110 to the device 30. This device can be a pressurized gaspropulsion device or a worm gear. It takes the regenerated catalyst backto the reactor 20 a via the pipe 120.

In some special forms of embodiment of these moving reactors, thereactors 20 a and 20 b can be part of the same unit having two separatestages.

The following examples illustrate the efficiency of the process of theinvention without limitation thereto.

EXAMPLE 1

The present example describes the effectiveness of the process,according to the invention, with respect to the elimination of thederivatives of the dibenzothiophene present in the partiallydesulfurized bases for fuels.

The samples of catalyst used are of two types, the catalysts formed froma single support and those to which are combined one or more metalsdeposited by impregnation. Table 1 below provides the specific surfacearea and porosity characteristics of each of them. TABLE I Catalyst TypeSpecific surface Pore size sample of support area (m²/g) (Angströms)Metal oxides C₁ SiO₂ 160 252 C₂ SiO₂ 140 300 WO₃ C₃ Al₂O₃ gamma 245 104WO₃ C₄ Beta zeolite 470 30 TiO₂ C₅ Mesoporous 1000 85 C₆ Mesoporous 83070 MoO₃ C₇ Al₂O₃ γ 210 95 WO₃

The catalysts C₂, C₃, and C₆ were obtained by wet impregnation with ametallic salt, respectively ammonium metatungstate and ammoniumhexamolybdate, in a concentration of 140 mg of metal per gram ofsupport, then dried and finally calcinated at a temperature of 500° C.

The catalyst C₄ was obtained by treating a beta zeolite withcommercially available titanium according to the procedure described inpatent EP 0,842,114.

To test the oxidation activity of these catalysts as a function of time,20 ml of catalyst is introduced into a 150 ml micropilot. A charge ofaverage distillates after hydrotreatment, containing 212 ppm of residualsulfur remaining from hydrotreatment, doped with 1,800 ppm of tert-butylhydroperoxide (tBHP), is circulated over the catalyst at an hourly spacevelocity (HSV) of 1 h⁻¹, under atmospheric pressure at a temperature of70° C. Samples are taken regularly during oxidation to measure theactivity of the catalyst over time. A comparative sample called T₁,corresponding to the use of a catalyst alone without peroxide, is alsomonitored.

In Table II below, the results are given of the effectiveness of thesecatalysts over time. TABLE II Total sulfur (ppm) after different periodsof operation Sample Catalyst 2 hrs 4 hrs 5 hrs 6 hrs T₁ C₁ 121 185 196202 X₁ C₁ 49 46 48 49 X₂ C₂ 28 14 9 16 X₃ C₃ 30 28 23 27 X₄ C₄ 18 16 1111 X₅ C₅ 35 32 38 35 X₆ C₆ 23 20 17 22 X₇ C₇ 34 31 25 31

After two hours of operation, these results confirm that, apart from theeffect due to the nature of the catalyst, the greater the catalyst poresize and specific surface area, the lower the sulfur content of thetreated hydrocarbons. Moreover, it is verified that the activity of thecatalyst increases when it is comprised of a metal oxide with support.However, after 24 hours, irrespective of the catalyst, a slight increaseis observed of the sulfur content of the desulfurized hydrocarbons,which may correspond to the beginning of clogging of the catalyst'spores, the sulfones and sulfoxides being attached thereto.

By this process, it is clear that the choice of a catalyst for theprocess of the invention is the result of a compromise between thenature of the catalyst, its specific surface area, and the size of thepores thereof.

EXAMPLE II

In this Example, the effectiveness of the catalyst is measured as afunction of the oxidation of the compounds.

The same process as in Example I is used, with catalysts C₁-C₆, and theformation is monitored of sulfones and sulfoxides with reference to thedibenzothiophene compounds, particularly the benzothiophene (BT),dibenzothiophene (DBT) and the 4,6 dimethyldibenzothiophene (DMBT), bygas chromatography equipped with a sulfur specific detector (SIEVERSprocess).

Table III below shows the results obtained. TABLE III Oxidizer % Sulfoneoxidation Catalyst concentration (eqS) BT DBT DMBT C₁ 3 80 78 81 C₂ 3 9095 93 C₃ 3 88 92 89 C₄ 3 96 99 95 C₅ 3 85 87 88 C₆ 3 92 94 93

These results show that there is a conversion of at least 80% of therefractory thiophenic derivatives into sulfones, with catalysts composedof a single support, and of more than 90% with catalysts composed ofsupports and at least a metal in the form of metal oxide inserted intothe matrix of the support or deposited on the support.

EXAMPLE III

The present example seeks to show, at the same time as the oxidation,the effect as a function of time of the adsorption of the sulfone andsulfoxide compounds on the oxidation/adsorption and regenerationsequences, and the effectiveness with reference to theoxidation/adsorption.

This was done with the C₃ catalyst under the operating conditionsdescribed in Example I on a middle distillate containing 44 ppm ofsulfur after hydrotreatment, and in the presence of 600 ppm of tBHP.

The results of the oxidation/adsorption are given in FIG. 3-1, when thecatalyst is fresh. After two days, the total concentration of sulfur inthe hydrocarbons increases substantially again to the initial value, inthe absence of the treatment, according to the invention.

The results of FIG. 3-2 correspond to monitoring the sulfur content ofthese same hydrocarbons when this same catalyst C₃, regenerated bycombustion, is used. The results obtained on a fresh catalyst are nearlyidentical to those obtained on the same regenerated catalyst.

These two graphs show the importance of the process of the inventionthat proposes an alternative operation of the same catalyst foroxidation/adsorption or for regeneration, the oxidation/adsorption timenaturally being adapted to the content in sulfur.

1. Process for selectively desulfurizing the thiophenic derivativescontained in the hydrocarbons produced from the distillation of crudeoil, refined or not, consisting of oxidizing the thiophenic sulfur atomsinto sulfones in the presence of an oxidizing agent, and of separatingthe sulfonated compounds from said hydrocarbons, this process beingcharacterized in that it includes at least a first step ofoxidation/adsorption by heterogeneous catalysis of the sulfurouscompounds, in organic medium, at a temperature of at least 40° C., inthe presence of an organic oxidizer from the family of peroxides andperacids and in the presence of a catalyst having a specific surfacearea greater than 100 m²/g and a porosity varying from 0.2 to 4 ml/g,and a second step of regeneration of the used catalyst, the regenerationstep always following the oxidation/adsorption step.
 2. Processaccording to claim 1, characterized in that the oxidation/adsorption andregeneration steps are carried out successively in the same reactor onthe same catalyst.
 3. Process according to claim 1, characterized inthat the oxidation/adsorption and regeneration steps are carried outsimultaneously in reactors (1, 2) arranged in parallel and operatingalternately for one and other steps.
 4. Process according to claim 1,characterized in that the oxidation/adsorption and regeneration stepsare carried out in two moving-bed reactors (20 a, 20 b) connected toeach other by the catalytic bed, one being used for the oxidation, theother for the regeneration.
 5. Process according to claim 1,characterized in that the oxidizing agent is selected from the groupconsisting of organic peroxides, organic hydroperoxides, and peracids.6. Process according to claim 1, characterized in that the catalystincludes a support selected from the group consisting of silicas,aluminas, zirconias, amorphous or crystalline aluminosilicates,aluminophosphates, mesoporous solids, activated carbon, clays, and theirmixtures.
 7. Process according to claim 6, characterized in that thecatalyst contains at least a metal selected from the group consisting oftitanium, zirconium, vanadium, chromium, molybdenum, iron, manganese andtungsten, this metal being introduced into the matrix of the support ordeposited in oxide form on the support.
 8. Process according to claim 1,characterized in that the catalyst contains from 0 to 30% by weight ofmetal in oxide form.
 9. Process according to claim 1, characterized inthat the catalyst is comprised of at least a support selected fromgamma-alumina, silica and silicic mesoporous solids andsilicoaluminates.
 10. Process according to claim 9, characterized inthat the supported catalyst is selected from catalysts containingtungsten on a support selected from silicas and aluminum oxides, aloneor in mixture.
 11. Process according to claim 1, characterized in thatthe oxidizer/total sulfur mol ratio in the hydrocarbons varies from 2 to20.
 12. Process according to claim 1, characterized in that the oxidizeris a compound with the general formula R₁OOR₂, in which R₁ and R₂ areselected identical or different from the group consisting of thehydrogen atom and the alkyl groups, linear or branched, having from 1 to30 carbon atoms, while R₁ and R₂ cannot be hydrogen simultaneously. 13.Process according to claim 12, characterized in that the oxidizer isselected from the group consisting of tert-butyl hydroperoxide anddi-tert butyl peroxide.
 14. Process according to claim 1, characterizedin that the oxidizer is a peracid of formula R₃COOOH, in which R₃ ishydrogen or a linear or branched alkyl group having from 1 to 30 carbonatoms.
 15. Process according to claim 14, characterized in that theoxidizer is selected from the group consisting of peracetic acid,performic acid, and perbenzoic acid.
 16. Process according to claim 1,characterized in that the catalyst regeneration step consists ofeliminating the formed deposits by washing or combustion.
 17. Processaccording to claim 1, wherein the hydrocarbons produced from thedistillation of crude oil are selected from the group consisting ofhydrotreated gasoils, kerosenes, and gasolines.
 18. Process according toclaim 8, characterized in that the catalyst contains from 0 to 20% byweight of metal in oxide form.
 19. Process according to claim 11,characterized in that the oxidizer/total sulfur mol ratio in thehydrocarbons varies from 2 to
 6. 20. Process according to claim 17,wherein the hydrocarbons produced from the distillation of crude oil aregasolines produced from catalytic cracking.